The layout constraints for drive trains in vehicles are increasing due to the growing number of accessories (power steering, air conditioning, . . . ), impact standards (frontal, pedestrian, . . . ) and pollution control standards (catalytic converters, particulate filters, . . . ).
The hybrid automotive drive combining heat and electric propulsion offers real advantages in reducing fuel consumption, but also in reducing pollutant gas emissions (CO2 emissions).
In designing a hybrid traction drive, in addition to the usual members associated with the heat engine, at least one dedicated electrical machine must be introduced into the engine compartment so that a pure electric drive mode can be provided.
To address this issue, some auto makers offer hybrid traction drives using transmission members to provide an infinitely variable transmission, also referred to with the Anglo-Saxon abbreviation “IVT”.
These transmission members consist mainly of a planetary gear train and two electrical machines.
There are several types of hybrid traction drive architecture: a so-called “series” hybrid traction drive, a so-called “parallel” hybrid traction drive and a so-called “series/parallel” (or power splitting) traction drive.
This latter architecture employs a planetary gear train coupled to the differential, and thus to the wheels of the vehicle, by means of a reduction gear. This architecture makes it possible to have an infinitely variable transmission that needs no clutch.
This type of architecture is described in particular in document WO 2005/007440.
The disadvantage of this solution is that firstly, the output is not always optimal because of the electrical power split needed to operate it, and secondly, because this architecture requires a thorough industrial retooling.
Another solution consists in sandwiching an electrical machine between the heat engine and the gearbox, with clutch-assisted torque transition.
The disadvantage of this other solution is that firstly, it increases the length of the drive train, and secondly, having the electrical machine positioned at the gearbox input reduces the hybrid operating potential.